How can I find and eliminate musty smells in my bedrooms and bathroom? These occur in the first floor above a crawlspace which frequently has standing water. I've posted separately about making a vapor barrier, but here I'd like to ask about the smells.

One of my bedrooms has smelled musty for 20 years. I tore down one of its external walls, did not find any mold, but replaced the 50-year-old insulation which smelled bad. Could that mild insulation smell have been seeping through the sheetrock into the room? Must I tear down the other external wall and replace its insulation?

The bathroom sheetrock is only two years old, yet smells very damp. Inside one wall, there are small gaps in the subfloor around the water and sewer pipes. This allows wet crawlspace air into the wall, but could that small quantity cause such a smell? Or could I check for a leaking sewer or water pipe? How can I treat the inside of this wall to remove the smell? I will seal it from below, but want to treat it first.

2 Answers
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It is absolutely unacceptable to have standing water in the crawl space of a pier and beam foundation. I would start with regrading around the house to direct surface water away from the foundation. The goal is to establish a swale about 4 ft from the foundation on any side where the ground slopes up from foundation.

Standing water in the crawl space will lead to a lot worse than a musty odor. It will eventually lead to rot in the beams, floor joists, and sub-floor.

Some people put drains under the soil in the crawl space leading to a sump from which water is pumped out and away from the foundation. Is the soil level in your crawl space below the level of the soil outside? Do you live in an area with a high water table and plenty of rain?

I agree with Jim and believe the standing water is the source of your problem. You would be surprised at the difference in your humidity levels and musty smell once the water is gone, not just a vapor barrier both, drain the water and a barrier.
– Ed BealFeb 7 at 15:36

I agree with Jim Stewart. However, you must remove the ground plastic and put plastic on the joists and beams. Then and only then, will you be able to alleviate the musty smells effectively and permanently. A simple fan in a crawlspace vent can exhaust and evaporate future moisture very efficiently.

Beyond that, any carpeting or even finish-floor in the rooms must be removed and replaced, after the house is isolated from the crawlspace moisture. Walls I wouldn't be so concerned about since they're sealed much better and vent themselves fairly well.